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Add fallback for pull by tag

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Some registries seem to be non-conformant and return a not found error
when pulling by digest (which docker now does all the time).
To work around this, fallback when all of the following are true:

1. Image reference is a tag
2. Tag->digest resolution succeeds
3. Fetch by resolved digest fails with a "not found" error.

This is intentionally not caching the manifests to reduce complexity for
this edge case.

Signed-off-by: Brian Goff <cpuguy83@gmail.com>
This commit is contained in:
Brian Goff 2020-12-03 21:15:18 +00:00
parent ab373df112
commit 495d623ae5
2 changed files with 54 additions and 6 deletions
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17
distribution/errors.go
View file

@ -112,6 +112,23 @@ func TranslatePullError(err error, ref reference.Named) error {
return errdefs.Unknown(err)
}
func isNotFound(err error) bool {
switch v := err.(type) {
case errcode.Errors:
for _, e := range v {
if isNotFound(e) {
return true
}
}
case errcode.Error:
switch v.Code {
case errcode.ErrorCodeDenied, v2.ErrorCodeManifestUnknown, v2.ErrorCodeNameUnknown:
return true
}
}
return false
}
// continueOnError returns true if we should fallback to the next endpoint
// as a result of this error.
func continueOnError(err error, mirrorEndpoint bool) bool {

41
distribution/pull_v2.go
View file

@ -343,16 +343,19 @@ func (p *v2Puller) pullV2Tag(ctx context.Context, ref reference.Named, platform
dgst digest.Digest
mt string
size int64
tagged reference.NamedTagged
isTagged bool
)
if digested, isDigested := ref.(reference.Canonical); isDigested {
dgst = digested.Digest()
tagOrDigest = digested.String()
} else if tagged, isTagged := ref.(reference.NamedTagged); isTagged {
} else if tagged, isTagged = ref.(reference.NamedTagged); isTagged {
tagService := p.repo.Tags(ctx)
desc, err := tagService.Get(ctx, tagged.Tag())
if err != nil {
return false, allowV1Fallback(err)
}
dgst = desc.Digest
tagOrDigest = tagged.Tag()
mt = desc.MediaType
@ -367,15 +370,42 @@ func (p *v2Puller) pullV2Tag(ctx context.Context, ref reference.Named, platform
"remote": ref,
}))
manifest, err := p.manifestStore.Get(ctx, specs.Descriptor{
desc := specs.Descriptor{
MediaType: mt,
Digest: dgst,
Size: size,
})
}
manifest, err := p.manifestStore.Get(ctx, desc)
if err != nil {
if isTagged && isNotFound(errors.Cause(err)) {
logrus.WithField("ref", ref).WithError(err).Debug("Falling back to pull manifest by tag")
msg := `%s Failed to pull manifest by the resolved digest. This registry does not
appear to conform to the distribution registry specification; falling back to
pull by tag. This fallback is DEPRECATED, and will be removed in a future
release. Please contact admins of %s. %s
`
warnEmoji := "\U000026A0\U0000FE0F"
progress.Messagef(p.config.ProgressOutput, "WARNING", msg, warnEmoji, p.endpoint.URL, warnEmoji)
// Fetch by tag worked, but fetch by digest didn't.
// This is a broken registry implementation.
// We'll fallback to the old behavior and get the manifest by tag.
var ms distribution.ManifestService
ms, err = p.repo.Manifests(ctx)
if err != nil {
return false, err
}
manifest, err = ms.Get(ctx, "", distribution.WithTag(tagged.Tag()))
err = errors.Wrap(err, "error after falling back to get manifest by tag")
}
if err != nil {
return false, err
}
}
if manifest == nil {
return false, fmt.Errorf("image manifest does not exist for tag or digest %q", tagOrDigest)
}
@ -818,11 +848,12 @@ func (p *v2Puller) pullManifestList(ctx context.Context, ref reference.Named, mf
return "", "", err
}
manifest, err := p.manifestStore.Get(ctx, specs.Descriptor{
desc := specs.Descriptor{
Digest: match.Digest,
Size: match.Size,
MediaType: match.MediaType,
})
}
manifest, err := p.manifestStore.Get(ctx, desc)
if err != nil {
return "", "", err
}